JPH04167969A - Method for evaporating flux for brazing - Google Patents

Abstract

PURPOSE:To extend the evaporation area of the flux, to accelerate its evaporation and to supply a satisfactory quantity of flux gas by evaporating the flux by using a vessel having projections projecting from a liquid level of molten metal to store the flux molten metal. CONSTITUTION:The projections 4a are put in an inconel crucible 4 having the projections 4a in a state protruded from the surface of the flux and further, the crucible 4 is stored in an evaporating device 3 in a heating furnace 1. N2 gas is introduced into a gas introduction pipe 6 for blowing and this gas is heated and the flux is evaporated while being blown against a liquid level of the flux molten metal 5 from a blowoff opening. Consequently, a large quantity of flux gas can be evaporated and the satisfactory quantity of flux gas can be supplied to a brazing furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method of evaporating brazing flux used for brazing aluminum condensers, radiators, car heaters, etc. for automobiles.

BACKGROUND OF THE INVENTION When manufacturing a brazed article such as the one described above using a brazing margin, it has conventionally been done to join constituent members using flux, except in the case of vacuum brazing. In this type of flux brazing, flux was generally applied to the surfaces of the joining parts as a suspension in water, etc., but the application process was complicated and the subsequent There were disadvantages such as a drying process being required and flux remaining on the surface of the bonded members after brazing, impairing the appearance.

Therefore, the present applicant first developed a brazing method that does not require the application of a suspension by supplying flux gas from the outside into the brazing furnace to create an inert gas atmosphere mixed with flux gas in the furnace. proposed a method of brazing inside (for example, Japanese Patent Application No. 1-217957).

Problems to be Solved by the Invention In order to supply such flux gas into the brazing furnace, flux gas evaporated from molten flux outside the brazing furnace may be placed on an inert gas as a carrier gas. This is carried out by transporting the flux into a furnace, but there are the following drawbacks when the flux is evaporated and gasified from the molten flux.

In other words, when flux is evaporated, an amount equivalent to the vapor pressure of the flux is obtained in a vacuum, but under atmospheric pressure using an inert gas as a carrier, the evaporation of the flux is suppressed by atmospheric pressure, and a sufficient amount of evaporation is obtained. The disadvantage was that it was not possible to obtain

For this reason, there was a problem in that a sufficient amount of flux gas could not be supplied to the brazing furnace, and good brazing could not be performed. In addition, in order to promote evaporation, sufficient heating energy must be supplied to the molten flux, and in order to maintain a small amount of flux gas in a gaseous state, it is necessary to install a flux gas evaporation device and piping to the brazing furnace. There were also problems such as the need to maintain high temperatures. In addition, problems such as the necessity to increase the size of the device arise due to the generation of a large amount of flux gas.

The present invention was made in order to eliminate such drawbacks, and an object of the present invention is to provide a method for evaporating wax flux, which makes it possible to obtain a sufficient amount of evaporation of flux even under inert gas pressure. shall be.

Means for Solving the Problems The above purpose is to evaporate flux from molten flux and supply the gasified flux to a brazing furnace by using a container protruding from the surface of the molten metal as a container for storing the molten flux. This is achieved by a method of evaporating wax flux, which is characterized by evaporating flux using a wax having one or more protrusions.

By evaporating the flux using a container that has one or more protrusions protruding from the surface of the molten metal as a container for storing the molten metal, the molten metal will evaporate due to surface tension at the interface with the protrusions. The liquid level rises, and the surface area of the molten metal increases compared to when no protrusions exist. Moreover, as the molten metal wets and spreads over the protrusions, the overall evaporation area expands and evaporation of the flux is promoted.

Example Next, this invention will be explained in detail.

In the mounting apparatus shown in FIG. 1, (1) is a heating furnace for evaporating flux, and (2) is a brazing furnace. The heating furnace (
1) is provided with an evaporator (3), and a crucible (4) is placed within this evaporator (3). One or more linear or plate-shaped protrusions (4a) are vertically provided inside the bottom wall of the crucible (4).

Then, the flux (5) is placed in the crucible (4), and the temperature of the heating furnace (1) is raised to boil the flux into a molten state. In this case, the flux molten metal (5)
The amount of flux must be adjusted so that the protrusion (4a) protrudes from the liquid surface. As a result, as shown in FIG. 2, the surface area of the molten flux (5) rises due to surface tension at the interface with the protrusion (4a), thereby expanding the surface area. In addition, the molten metal wets and spreads over the protrusion (4a), which results in an expansion of the evaporation area, making it possible to enjoy the advantages of the present invention. The type of flux is not particularly limited, and any eutectic composition of KF and AQ F3, fluoride flux such as KAQF4, or chloride flux may be used, but in terms of non-corrosion, It is preferable to use a fluoride-based flux, and it is particularly preferable to use KAQF4, which is easily evaporated.

A blowing gas introduction pipe (6) is inserted into the evaporator (3) through the earth walls of the heating furnace (1) and the evaporator (3). Gas inlet pipe (6) for spraying
It is preferable that the tip outlet of the molten flux (5) be placed directly opposite the surface of the molten flux (5). In this state, inert gas such as N2 gas is supplied from the outside to the gas introduction pipe (6), and the gas is sprayed from the outlet onto the surface of the molten flux (5) using the supplied pressure. By this spraying, the flux vapor that has reached a saturated vapor pressure near the surface of the molten metal is blown away, and the evaporation of new flux from the molten metal is further promoted. Note that spraying this inert gas onto the surface of the molten metal is not an essential requirement of the present invention.

The flux thus evaporated into gas is transferred to the evaporator (3).
It is mixed with inert gas inside to form a mixed gas. Evaporator (
A mixed gas introduction pipe (7) communicating between the evaporator and the brazing furnace (2) is open in the interior of the evaporator (3), and the mixed gas in the evaporator (3) is fed through the mixed gas introduction pipe (7). The solder is then sent to a brazing furnace (1) with an inert gas atmosphere, and the brazing furnace is adjusted to an inert gas atmosphere containing flux gas. Brazing is then performed in this atmosphere.

Next, in order to confirm the effects of the present invention, the following tests were conducted.

[Example Using KAflF4 as the coflux, this KAΩF4
is placed in an Inconel crucible (4) having cleaning protrusions (4a) as shown in Fig. 1 with the protrusions (4a) protruding from the surface of the flux, and the crucible is placed in a heating furnace (1). was placed in the evaporator (3).

Then, for spraying, add 22/2 N2 gas to the gas introduction pipe (6).
The KAΩF4 was heated to 740° C. and evaporated in an atmospheric pressure atmosphere while introducing the gas at a rate of 10 min and blowing this gas onto the surface of the molten flux (5) from the outlet. Spraying is carried out between the outlet of the gas inlet pipe (6) and the molten metal (5).
) was set at 100 In.

Next, the flux gas evaporated as above was mixed with a moisture content of 1
A N2 gas atmosphere of 100 ppm and an oxygen concentration of 10 ppm was supplied to the brazing furnace (2) to create an N2 gas atmosphere containing flux gas inside the brazing furnace. Then, in this atmosphere, a heat exchanger assembly in which the aluminum tubes and fins were temporarily assembled was heated at 600° C. for 5 minutes and brazed. The tube is made of extruded A1100 aluminum alloy with a wall thickness of 0.88 mm, and the fins are made of A3003 aluminum alloy as the core material and AΩ-10 wt% Si alloy as the skin material, with a clad ratio of 15% and a thickness of 0.8 mm. A 15 m double-sided plating sheet was used.

[Comparative Example] On the other hand, as a comparative example, as shown in FIG.
′) without any protrusions, and
Flux was evaporated under the same conditions as in the above example except that the gas introduction pipe (6') to the evaporator (3) was installed in a horizontal blowout state so that the N2 gas did not directly hit the molten flux (5). Ta. After introducing this flux gas into the brazing furnace (2), brazing was performed under the same conditions as in the example.

For each of the above [Example] and [Comparative Example], the amount of flux gas supplied to the brazing furnace (2) (the amount of flux gas for N2 gas conversion converted to room temperature) was measured, and the heat exchanger The external appearance and brazing condition of the re-brazed were visually observed.

The results are shown in Table 1.

Table 1 (Note 1) ○...The surface was clean.

X: The surface was discolored to brown.

(Note 2) ○... Sufficient fillet was formed.

x: Formation of fillet was insufficient.

As can be seen from the above test results, in the comparative method, the flux gas in the brazing furnace was insufficient due to the small amount of flux evaporation, and good brazing could not be achieved, whereas in the method of the present invention, good brazing could not be performed. With this method, sufficient flux gas could be evaporated and supplied to the brazing furnace, and it was confirmed that good brazing was achieved.

Effects of the Invention As described above, this invention provides a container that protrudes from the surface of the molten metal as a container for accommodating the molten flux when the flux is evaporated from the molten flux and the gasified flux is supplied to the brazing furnace. Since the flux is evaporated using a tool or a tool having multiple protrusions, the surface area of the molten flux rises due to surface tension at the interface with the protrusions, expanding the surface area. . In addition, as the molten metal wets and spreads over the protrusions, the evaporation area as a whole is expanded, and as a result, evaporation of the flux can be promoted. For this reason,
A large amount of flux gas can be evaporated even under atmospheric pressure using an inert gas as a carrier, and a sufficient amount of flux gas can be supplied to the brazing furnace.

In addition, since the evaporation of flux gas can be promoted, it is not necessary to supply a large amount of heating energy to the molten flux, and the temperature of the flux gas evaporation equipment and piping to the brazing furnace can be maintained at a high temperature. There is no need to use special materials as equipment materials; stainless steel or the like will suffice. Further, it is possible to eliminate the inconvenience of increasing the size of the device in order to ensure the amount of evaporation.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an apparatus for implementing the present invention, FIG. 2 is an enlarged view of Ruriho shown in FIG. 1, and FIG. 3 is a schematic configuration diagram showing an apparatus for implementing the comparison method. . (1)... Heating furnace, (2)... Brazing furnace, (4)...
・Crucible (container), (4a) ・Protrusion, (5)・
...Flux molten metal. that's all

Claims (1)

[Claims] When evaporating flux from molten flux and supplying this gasified flux to a brazing furnace, a container having one or more protrusions protruding from the surface of the molten metal is used as a container for storing the molten flux. A method of evaporating flux for brazing, characterized by evaporating the flux using a method.